The patch titled
Subject: zsmalloc: add a LRU to zs_pool to keep track of zspages in LRU order (fix)
has been added to the -mm mm-unstable branch. Its filename is
zsmalloc-add-a-lru-to-zs_pool-to-keep-track-of-zspages-in-lru-order-fix.patch
This patch will shortly appear at
https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches/zsmalloc-add-a-lru-to-zs_pool-to-keep-track-of-zspages-in-lru-order-fix.patch
This patch will later appear in the mm-unstable branch at
git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm
Before you just go and hit "reply", please:
a) Consider who else should be cc'ed
b) Prefer to cc a suitable mailing list as well
c) Ideally: find the original patch on the mailing list and do a
reply-to-all to that, adding suitable additional cc's
*** Remember to use Documentation/process/submit-checklist.rst when testing your code ***
The -mm tree is included into linux-next via the mm-everything
branch at git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm
and is updated there every 2-3 working days
------------------------------------------------------
From: Nhat Pham <nphamcs@xxxxxxxxx>
Subject: zsmalloc: add a LRU to zs_pool to keep track of zspages in LRU order (fix)
Date: Wed, 23 Nov 2022 11:17:02 -0800
Add a comment explaining the mapping check for LRU update.
Link: https://lkml.kernel.org/r/20221123191703.2902079-2-nphamcs@xxxxxxxxx
Signed-off-by: Nhat Pham <nphamcs@xxxxxxxxx>
Suggested-by: Johannes Weiner <hannes@xxxxxxxxxxx>
Suggested-by: Sergey Senozhatsky <senozhatsky@xxxxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
mm/zsmalloc.c | 18 +++++++++++++++++-
1 file changed, 17 insertions(+), 1 deletion(-)
--- a/mm/zsmalloc.c~zsmalloc-add-a-lru-to-zs_pool-to-keep-track-of-zspages-in-lru-order-fix
+++ a/mm/zsmalloc.c
@@ -1289,7 +1289,23 @@ void *zs_map_object(struct zs_pool *pool
zspage = get_zspage(page);
#ifdef CONFIG_ZPOOL
- /* Move the zspage to front of pool's LRU */
+ /*
+ * Move the zspage to front of pool's LRU.
+ *
+ * Note that this is swap-specific, so by definition there are no ongoing
+ * accesses to the memory while the page is swapped out that would make
+ * it "hot". A new entry is hot, then ages to the tail until it gets either
+ * written back or swaps back in.
+ *
+ * Furthermore, map is also called during writeback. We must not put an
+ * isolated page on the LRU mid-reclaim.
+ *
+ * As a result, only update the LRU when the page is mapped for write
+ * when it's first instantiated.
+ *
+ * This is a deviation from the other backends, which perform this update
+ * in the allocation function (zbud_alloc, z3fold_alloc).
+ */
if (mm == ZS_MM_WO) {
if (!list_empty(&zspage->lru))
list_del(&zspage->lru);
_
Patches currently in -mm which might be from nphamcs@xxxxxxxxx are
zsmalloc-consolidate-zs_pools-migrate_lock-and-size_classs-locks.patch
zsmalloc-add-a-lru-to-zs_pool-to-keep-track-of-zspages-in-lru-order.patch
zsmalloc-add-a-lru-to-zs_pool-to-keep-track-of-zspages-in-lru-order-fix.patch
zsmalloc-add-zpool_ops-field-to-zs_pool-to-store-evict-handlers.patch
zsmalloc-implement-writeback-mechanism-for-zsmalloc.patch
